The Role of KCNQ4 Channels in Progressive Hearing Loss

Several forms of hearing loss in humans are related to mutations in genes coding for specific ion channels located in the inner ear. In particular, mutations in KCNQ4 channels cause progressive hearing loss in some human patients. However, little is known about the molecular and cellular mechanisms underlying this phenomenon. Liping Nie, Ph.D., will investigate how mutations in these ion channels lead to disruption of KCNQ4 functions and ensuing hearing loss.

Noise-induced hearing loss (NIHL) is the second most common form of hearing loss, after presbycusis. Currently, there are no medications to treat NIHL. Jianxin Bao, Ph.D., and colleagues have found that a family of anticonvulsive drugs that blocks T-type calcium channels, can significantly prevent NIHL in mice. Bao will further investigate how these drugs can prevent and/or treat NIHL, and will also look at the effects of these drugs on mice without the specific T-type calcium channels. The ultimate goal of his research group is to develop methods for prevention and treatment of hearing loss based on identifying molecular targets involved in hearing loss.

Determination of Redox State in Hair Cell Mitochondria

Many forms of sensorineural hearing loss are due to the death of hair cells-the specialized cells in the cochlea that translate sound waves into electrical impulses which are translated as sound in the brain. However, little is known about why hair cells die. Richard Hallworth, Ph.D., and colleagues believe that hair cell death may be caused by oxidative damage due to the generation of free radicals. They will investigate the metabolism of various hair cell types (and therefore, the generation of oxidative damage).

The Effects of Selective Hair Cell Damage on Temporal Envelope Coding in the Auditory Nerve

Two patients with similar audiograms (a graph depicting the degree of a patient’s hearing loss at different frequencies) can have very different speech recognition abilities. This variability among patients provides a challenge to audiologists in fitting hearing aids to individual patients. It is likely that much of this variability in perception arises from differences in the root physiological causes of hearing loss in each patient. Previous research has suggested that many common forms of cochlear hearing loss arise from a mixture of outer-hair-cell and inner-hair-cell damage (the two types of auditory sensory cells in the cochlea). While functional damage to each type of hair cell contributes to hearing loss as measured in an audiogram, outer- and inner-hair cells have very different effects on other response properties that are significant for speech perception. Thus, it is very difficult to infer the degree of outer- and inner-hair-cell damage from a patient’s audiogram.

Michael Heinz, Ph.D. seeks to develop a more detailed understanding of the differential effects of OHC and IHC damage on the neural coding of perceptually relevant sounds in the auditory nerve. Specifically, he will study the neural coding of slowly-varying modulations in sound amplitude (temporal envelope), which have been shown to be perceptually relevant for speech perception, pitch extraction, and sound localization. It is hoped that these results will offer new insight towards the development of clinically viable tests that would allow clinicians to diagnose the underlying configuration of OHC and IHC damage in individual patients.

Characterization of a de novo Protein Expressed in the Mammalian Cochlea

Hair cells convert the mechanical force of sound waves into electric signals that are eventually translated in the brain as sound. The key element in the transformation process is the mechano-electric transducer (MET) apparatus located near the top of stereocilia. A cadherin molecule (CDH23) is believed to be part of the MET apparatus. Jing Zheng, Ph.D., will investigate the interaction between CHD23 and a new protein they have previously discovered in hair cells.

in the news

April 3, 2015 - “Blue Skies” is the tale of Tom, a building inspector who is diagnosed with significant hearing loss, and the story of how that simple problem affects his work and personal life. He must come to terms with what he stands to lose – not just his hearing, but his most important connection to the past.

April 3, 2015 - We are proud to announce that Brian Tyler, award-winning film score composer, actively supports the work of the American Hearing Research Foundation.

The American Hearing Research Foundation is a non-profit foundation that funds research into hearing loss and balance disorders related to the inner ear and is also committed to educating the public about these health issues.